MOF Formation vs. Reversible High Ligand Uptake in Anhydrous Halides: Two Opposing Aspects of 3∞[La2Cl6(4,4′-bipy)5]•4(4,4′-bipy)

Construction of the framework structure (3)(infinity)[La2Cl6(bipy)(5)]center dot 4bipy (1), bipy = 4,4'-bipyridine, C10H8N2, is achieved by reaction of the anhydrous halide LaCl3 with molten 4,4'-bipyridine. Five equivalents of bipyridine are Used For the framework construction linking LaCl3 units to give all extended, three-dimensional MOF. Furthermore, four additional equivalents of bipyridine per LaCl3 unit are incorporated within the crystalline MOF, which is thereby completely filled with bipy molecules. This compound formation results in the extraordinary high uptake offline equivalents of bipyridine per equivalent of the formula and a volume increase of eight times the volume of LaCl3. Further heating of the MOFs results in a stepwise release of all nine equivalents of bipyridine and reformation of the anhydrous chloride at 425 degrees C. Formation and disassembly can be run in cycles and are reversible. Thus two interesting yet opposing aspects are the reversible construction and disassembly of the MOF framework.